Mayer started at designated hitter and went 0-for-4 in Monday's 5-2 win over the Twins.
Mayer came up empty at the plate, striking out in all four at-bats in his team debut. Monday marked the 23-year-old's first big-league action since June 25. He initially dealt with a left forearm stress reaction with the Red Sox before suffering a bone bruise in his right foot during rehab after being traded to the Giants. In 232 big-league plate appearances in 2026, Mayer is hitting .215/.277/.306 with three homers, 22 RBI, 19 runs and three stolen bases.